Incandescent lamp comprising two



INCANDESCENT LAMP COMPRISING TWO FILAMENT WIRES, MORE PARTICULARLY FOR CAR SEARCH LIGHTS Filed April 26, 1952 IIVVENTOR Karl Bohme 1 at 4, for example by welding, to the screen.

United States Patent INCANDESCENT LAMP COMPRISING TWO FILA- MENT WIRES, MORE PARTICULARLY FGR CAR SEARCH LIGHTS Karl Biihme, Aachen, Germany, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee, patent dedicated to the public insofar as it relates to lamps and lamp parts to the extent stated in document recorded in the U. S. Patent Ollice April 13, 1954 Application April 26, 1952, Serial No. 284,501 Claims priority, application Germany October 6, 1951 2 Claims. (Cl. 313-272) The invention relates to electric incandescent lamps. More particularly, the invention relates to a two-filament electric incandescent lamp, generally used in automobile headlamps, in which one filament is positioned in front of a reflector slightly above the axis of the lamp and in the direction of a shielding cap for providing a low beam While the other filament is positioned coaxial with the lamp axis and provides distant illumination.

It is an object of the present invention to simplify the construction of such lamps by providing a novel connection between each of the filaments and a common supply conductor which also serves as a filament support without requiring correction of the position of the filaments in manufacture of the lamps.

According to the invention, in an electric incandescent lamp comprising two filaments, the directions of winding 7 of the coiled filaments superposed in their direction of length are opposite such that the filament ends secured to the common terminal wire extend along the same tangential plane of the filaments.

In order that the invention may be readily carried into efiect, it will now be described in greater detail with reference to the accompanying drawing, given byway of example, in which Figure 1 is a side view of a lamp in accordance with the invention;

Figure la is a reduced scale, sectional view on line AB of Figure 1; and

Figure 1b is a reduced scale, sectional view on line C-D of Figure 1.

The glass bulb shown in Fig. 1 contains a screen 2 supported only by a supporting wire 2a consisting of an electrically conducting terminal wire. The screen 2 is concave. The hollow member is to be imagined to lie behind the plane of, the drawing. A filament 3 is connected The other end of 'the filament 3 is similarly connected at 5 to the terminal wire 6. Below the auxiliary coil 3 extendsthe main filament 7, whose top 8 is also connected to the wire 6, its bottom end being secured to a terminal wire 9. The filaments 3 and 7 are arranged co-axially with the axis of the lamp. As an alternative, this only holds with respect to the filament 7. The filament 3 extends slightly beyond the axis of the lamp, so that in the drawing it would extend in front of its plane.

According to the invention the filament coils constituting the glowing members 3 and 7 have difierent directions of winding. In the present example, the filament coil of the lower filament 7 is wound counterclockwise and that of the glowing member 3 is wound clockwise, thus achieving that at 5 and 8 the filament ends attached to the common terminal wire 6 extend along the same plane and permit attachment without bending the tungsten wire. In this manner it is also achieved that the common terminal wire 6 must be provided laterally of the axes of the glowing members and consequently of the axis of the lamp, hence no troublesome shadows are cast when controlling, by optical projection of the lamp system, the spacings to be maintained in manufacturing the lamp.

In order to elucidate the positioning of the various parts of the stem, each of Figures 1a and 1b show on a reduced scale a plan view obtained by sections along the straight lines AB and CD.

What I claim is:

1. An electric incandescent lamp comprising two approximately coaxially-mounted axially-spaced oppositelywound filaments, a common conductor extending adjacent and parallel to said filaments and supporting the same in their operative position, and terminal means for said filaments including adjacent terminal means to connect each of said filaments to said common conductor, said adjacent terminal means each, extending substantially entirely in a plane common to both of said filaments and tangent to said common conductor.

2. An electric incandescent lamp comprising a bulb having a central axis, two axially-spaced oppositelywound filaments in said bulb, said filaments being mounted substantially coaxially with each other and with the bulb, a common conductor extending adjacent and parallel to said filaments and supporting the same in their operative position, terminal means for said filaments including adjacent terminal means to connect each of said filaments to said common conductor, said adjacent terminal means each extending substantially entirely in a plane common to both of said filaments and tangent to said common conductor, and a cup-like hollow mem' ber half-surrounding one of said filaments.

References Cited in the file of this patent UNITED STATES PATENTS 

